I had the same results
This cheese did not pop for me. I was bouncing between multiple boxes, single player and co-op....
1. I deleted the game and its save files
2. I erased the cache memory from the hard drive
3. Downloaded again
4. Only played single player on ONE xbox
5. Your advice about running through the game and saving the fights for the green skeletons (2000 pts each) in the end was brilliant. Thank you.
6. Cheese be poppin!!!
Hind sight, maybe this cheese isn't gitchy as much as it is touchy.